1. Field of the Invention
The present invention relates to an image recording material which can be used as a planographic printing plate. More particularly, the present invention relates to a negative type image recording material suitably used as a planographic printing plate which is capable of directly producing a printing plate using an infrared laser based on digital signals output from a computer or the like.
2. Description of the Related Art
Conventionally, as systems for producing a form plate directly from digital computer data, there have been proposed (1) a system using an electrophotographic method; (2) a system using a photopolymerizable compound, which polymerizes by being exposed to a laser which emits blue or green light; (3) a system using a recording material in which a salt is laminated on a photosensitive resin; and (4) a system using a silver salt diffusion transfer method.
However, the system using an electrophotographic method (1) above has complicated image formation processes such as charging, exposure, developing, and the like and therefore the apparatus thereof becomes sophisticated and large. In a system using a photopolymerizable compound (2) above, since a form plate which is highly sensitive to blue or green light is used, it is difficult to handle in an illuminated room. In methods (3) and (4), since a silver salt is used, there are the disadvantages that processes such as developing and the like become complicated and the waste solution naturally contains silver.
In recent years, laser technologies have developed remarkably. In particular, high output and compact solid-state lasers and semiconductor lasers emitting infrared rays of a wavelength of 760 nm to 1,200 nm are readily available. These lasers are very useful as a light source for recording in the direct production of a form plate from digital computer data. However, since most practical useful photosensitive recording materials are sensitive to visible light having a wavelength of 760 nm or less, image recording cannot be carried out with these infrared lasers. Therefore, a material recordable with an infrared laser is desired.
Examples of such image recording materials capable of recording an image with an infrared ray laser include a recording material comprising an onium salt, a resol resin, a novolak resin, and an infrared ray absorbing agent disclosed in Japanese Patent Application Laid-Open (JP-A) No. 7-20629. Furthermore, Japanese Patent Application Laid-Open (JP-A) No. 7-271029 discloses a recording material comprising a s-triazine substituted with haloalkyl, a resol resin, a novolak resin, and an infrared ray absorbing agent. However, form plates formed with these image recording materials have problems such as stains which are formed in a nonimage portion when they are stored for a long period of time at a high temperature and high humidity, followed by image formation and printing. In addition, the sensitivity tends to fluctuate depending upon heat treatment conditions after exposure, resulting in deterioration of the durability to a level lower than that required for printing in a part of the plate surface due to unevenness of heat treatment in the exposure of a large image.